SpaceX tests black satellite to reduce ‘megaconstellation’ threat to astronomy
nature.com
nature.com
The viewing window is actually pretty small. For most of the night the satellites are not visible because they are in Earth's shadow. There is an impact on astronomy but it is being overstated by journalists hungry for yet another "Big Tech bad" story.
Indeed, and let's not forget that Elon has upset a lot of applecarts with SpaceX and Tesla.
But those are a special case, air cherenkov telescopes are looking for "less weird" particles like photons or protons. Those can only be seen looking up, since the primary particles moving down focuses the cherenkov light down in a narrow cone.
Basically a big bubble filled with the most useful gas for this + bunch of photodetectors inside at the appropriate places. You could also make the whole detection chamber much larger, than the ~30 km (?) of reasonably thick atmosphere you get on Earth.
Another reason is that they're only launching one and it has to work perfectly the first and only time it's launched. That level of reliability in a one-off product is incredibly expensive to achieve. With dramatically cheaper launches it would make sense to launch a much larger number of less reliable but much less expensive telescopes.
Another reason is politics, but SpaceX can't solve that one.
What if... SpaceX made up for the pollution they introduce by making the Starlink satellites look up the other way and push the captured data back to earth? The lens and CCD would be small, but with the massive volume (and clear sky) it could add up. Like the amateur set ups using an array of consumer grade cameras.
A rule of astronomy is that if you can see it with your eyes near a city than it’s really really fucking bright, if you can see it with your eyes in the wilderness after your eyes have adjusted for 10 minutes, than it’s still extremely bright.
Bright, fast-moving things are pretty terrible.
Even if Starlink doesn’t kill astronomy, the next 4 companies with similar deployment will definitely exclude types of sciences and ruin billions of dollars of investments in new observatories.
It will likely affect some earthbound astronomy significantly, but much (most?) of the most important work in modern astronomy is satellite based.
I'm on the fence on this whole issue. It's not exactly clear what impact it will have on astronomy. Nor what impact it will have on making the internet pricing and availability. Where I used to live, the only options for internet access were expensive and really bad, the positive impact this might have is potentially quite big.
It's hard with a story like this to suss out what the long term effects will be so it's a big grey area.
/s (jeez, your sense of humor folks...)
Of course, the reason why people who enjoy lecturing others about why something can't be done differently or shouldn't be done differently seem to gravitate to a site called "Hacker News" is one of those universal mysteries that can't be answered with a computer or a telescope.
Don't fight the people who are trying to fix this.
I'm not an astronomer but I'm not convinced that that's the case. The number of space telescopes pales in comparison to the number of terrestrial observatories. Moreover, advances like adaptive optics have done a lot to close the gap between ground and space capabilities (for optical telescopes). Even once you've invested in expensive tech like adaptove optics, a telescope in space still costs an order of magnitude more than one on the ground (thats being really conservative. JWST has already cost ~10x more than the most expensive ground telescope ever, and the thing hasn't even launched yet)
There were a few space based radio telescopes in the past, but I don't think there are any now. Imagine building something like the Arecibo Observatory[1] or VLA[2] in space. And speaking of the VLA, some of the techniques for getting high quality results (e.g. interferometry without physically conjoining the receivers) are difficult if not impossible to do in space.
[1]: https://en.wikipedia.org/wiki/Arecibo_Observatory
[2]: 27 of these guys, which are able to move around precisely on rails to generate constructive interference with the different waves they're receiving: https://public.nrao.edu/wp-content/uploads/2016/04/vla_panor...
You need old distant objects for cosmology, observing the structure if the universe, big bang and stuff. You need variability for finding exoplanets, measuring distance and observing transitions such as supernovae.
Oh, and then a huge part is taking spectra, which means bouncing the light directly off a grating. Filtering transients is hard to impossible there. You need spectra for relative motion, magnetic fields, composition of matter and radiation and of course temperature.
Needing such filters would set astronomy back a few decades
You replied "Optical, RF, or Xray?"
Then I said, "Let's start with optical." but then you disappeared!
So, what's your solution for long-slit optical spectroscopy?
To be clear, I think we're well in the realm of academic discussion; no one is stopping any global constellation due to astronomy concerns. As I've said many times in this thread and elsewhere, I think it's a growth opportunity for the astronomy community to move towards space based observation platforms, and with the plummeting cost of lift (ie SpaceX Falcon and Starship) I don't think that's an unreasonable position to hold.
I'm not entirely certain what the balance is here. I don't think my post made it clear that I'm not certain how big the effect would be, only that there is a tradeoff here which is hard to quantify.
I do know there is a lot of significant astronomy done by space telescope and that the importance of space astronomy is only growing.
Seems to me the answer is that those who benefit from the new satellite constellations (SpaceX, etc) should finance additional investment in astronomy to mitigate the effects.
I'd trade amateur ground astronomy for that.
There are plenty of good pictures on wikipedia already, do looking at those compare to going out on a clear night and looking at the stars yourself?
Imagine if a painter in Greece in some century BC convinced his fellow Grecians that building a harbor in the cove by their town was a bad idea because it ruined his paintings of the cove. How was he supposed to look at the marine life if you stuck wood and industry in the water???
I'd be curious to know what the impact is on impactful amateur astronomy (as opposed to backyard hobbyists who are just engaged for personal pleasure). I know some amateurs use images created by public telescopes, I'm not sure how much meaningful work is done by amateurs using backyard equipment anymore.
Not being dismissive, genuinely curious.
A decent number of asteroids and comets are still found by backyard astronomers.
"Since professional astronomers do not have the time or the resources to monitor every variable star, astronomy is one of the few sciences where amateurs can make genuine contributions to scientific research." [0]
[0] https://en.wikipedia.org/wiki/American_Association_of_Variab...
Former astronomer here. I would argue that the importance of space astronomy is actually decreasing. Satellite telescopes are most important at wavelengths that the Earth's atmosphere absorbs like IR, UV, and X-ray. At visible wavelengths satellite telescopes have been much less important over the past couple of decades due to the development of adaptive optics.
The main reason to put a visible wavelength telescope in space is that you avoid the smearing out of the source by the atmosphere. Adaptive optics solves this problem by correcting for the distortions induced by the atmosphere and bringing images to resolutions that are comparable to (though still not quite as good as) what you can achieve in space.
Since space telescopes no longer have the advantage of much greater resolution, there's much less of a compelling reason to use them for most research problems. (Some questions, of course, can only be tackled by using the highest resolution available.) On every other dimension space-based telescopes are inferior to ground-based telescopes. They are more expensive by many orders of magnitude, much, much smaller, and they cannot be changed once they're up (at least not easily). By contrast a ground based observatory can get substantially better over the course of a year by installing better detectors.
IMO, over the next 30 years space based telescopes are going to play an ever larger role.
You're going to have to point out which source you pulled that out of! As a simple example, more than half of the Nobel prizes awarded for astronomy since 2000 are for discoveries made with ground based detectors. And of those awarded to satellite experiments, none was actually competing with a ground based experiment, so satellites mainly bring different, not better, capabilities.
When I encounter this phrase I think of things like the neutrino detector in Antarctica, which of course isn't affected by satellites at all. How much contemporary astronomy relies on visible-light telescopy?
Not true at all. Ground based is much cheaper and easier to maintain and reconfigure with new and different equipment. Just look at the cost of the upcoming >30m telescopes vs the James Webb or Hubble.
And since you are going to spend so much money to launch it, you also add extra hardware to do other type of observations, so the cost of the telescope balloons upward but you are get more bang for the buck.
If on the other hand you have cheap launches then you can send up the minimum telescope needed since you can always send up a better one or even a very different one if you later discover the need.
Today because of high costs, we need to design the scopes to meet all the possible needs we can think of and afford, result very expensive space scopes.
Why make this more expensive than it needs to be? Researchers are already strapped for cash.
The key point is usable observation time. Our current handful of satellite telescopes provide 24h of time a day. Each terrestrial telescope provides maybe 8h. However, there are a magnitude more telescopes on Hawaii alone than in space. You would need to get a hundred satellite telescopes to begin to replace earthbased observation time.
And that doesn't even begin to talk about the possible instruments, mirror sizes, astronomical costs of buulding and running satellites, etc.
Satellites are invisible if they're in the Earth's shadow. By the time useful observation can begin, there's an enormous swath of the sky that will have zero visible satellites in it.
Diversify your observation targets. There's more than one interesting thing to science at any given moment. If that means spreading out your observations so you spend two hours a night observing four targets as opposed to four hours a night on two targets, so be it.
At the very worst, this means astronomers will need to do more work during the day shift scheduling and prioritizing. This isn't a new problem. I remember reading a back page article in Astronomer magazine sometime in the late 90s with a page of BASIC code. Someone wanted to optimize a computer controlled telescope to make one observation of 100 or so stars every night. You need to roughly minimize the total Manhatten distance between every two observations, while also eliminating observations below the horizon and penalize observations low in the sky. So the author wrote a program to roughly approximate the traveling salesman problem with the additional constraints. In the 90s. In BASIC. In one page. It might be NP complete to get the perfect solution, but good enough is pretty good.
Add an additional constraints penalising observations where they might be impacted by satellites. Hire an intern working on their degree who's taken an optimization course and have them do it for you.
We're going to have to start thinking bigger if we want to leave this rock. Might as well start now.
The real risk is Elon's companies dissolving and the satellites adding pollution for no real gain. If I could trade observatory time for (working) world-wide internet, I'd take the latter with no hesitation.
As much as I sympathize, most of the cosmos aren't really going anywhere. It'll be there after we build hundreds of telescopes.
There is no way to see Starlink at night. You can potentially see them for a short period around twilight.
The satellites you can easily see at any time are much higher up.
The time window is limited, yes. So it is not the end of the world. It is still a problem.
Starlink satellites directly overhead are in sunlight for about 1.5 hours after sunset, and the same before sunrise. Including observing on an angle, you probably lose 4 hours per night out of 12. With 300km satellites, you probably lose 3 hours. I think the situation will be worse away from the equator in summer.
Why is that? Almost everything astronomy studies isn't fast-moving. Shouldn't it be easy to filter out that noise?
First is the impact to "professional astronomers", and from what I've seen this group won't be impacted nearly as much as the other. This group has the ability to use satellite based telescopes, or has the tech already to be able to filter/post-process the images to remove satellites, planes, meteor showers, and any other stuff that might get in the way.
Then you have "amateur astronomers", this groups is likely to be impacted by starlink. This group doesn't have access to the digital filtering stuff that the "big guys" do, from what i've seen, most of the people in this group just use normal long-exposure setups and adding in a processing step would mean a pretty significant change to their process, and probably a lot of additional costs.
Even still, the impact to amateur astronomers seems limited to when the sats are in sunlight, which traditionally isn't a super popular time for stargazing (although I may be wildly wrong on this, as I've read that these sats are removing up to 1/3 of the normal viewing time for some astronomers, so don't take this as gospel), and I still think the impacts will be a lot less doom and gloom than some are saying, but I still hope that SpaceX can work with the astronomy community to see if there are solutions or mitigations that can help everyone out.
Filtering is less advanced, but masking outliers (and their neighbors) and replacing them with an average of the others isn't advanced filtering.
It's annoying the way getting cut off in traffic is annoying, not the way getting T-boned is annoying.
If we were to employ the reversal test[1], the concern about astronomy would be a non-problem. Imagine if the entire planet was covered by the equivalent of 4G cell networks. And imagine if some astronomers asked us to destroy those networks so that some of their work could be made more convenient. Imagine all of the people affected by this network. All of the lives saved by emergency calls, all of the remote locations made digitally accessible to the rest of humanity, all of the scientific experiments in jungles, deserts, tundra… cameras and microphones and sensors reporting data through this global satellite network… imagine all of that destroyed so that some astronomers could be relieved of an inconvenience. That is absurd. Yet that is the world that some people want to live in.
It's so clear to anyone whose view isn't so parochial, so local in time and space, so blinkered by where and when they were born. Does anyone think that astronomers will still be preventing the launch of satellite constellations in the year 2100? In 2200? In 2500? Clearly not.
I'd rather the improvement happen in my lifetime than after. Launch away.
Fast-moving = more likely for it to traverse your field of view while the shutter is open
Once the sun is set in their orbit, they should be invisible both to the eye and telescopes.
These are not geosynchronous satellites, but instead are 200-500 miles above the Earth, moving many, many thousands of mph. No, it isn't blocking anything 100 light years away unless your shutter speed is in the single-digit nanoseconds.
In fact if, as you believe, these satellites would actually occlude things beyond them, they sound very useful for calibration and education.
That's where it can shade 24h/day.
Moreover, I think mega-constellations will actually be a boon for astronomy. Think of it as a platform, while initial iterations will be focused on communication systems, what is stopping them from adding sensor packages looking both inwards and outwards? They already have the bandwidth to downlink all of that. Once on the ground those streams could be combined to produce datasets of unprecedented coverage and fidelity.
Second, astronomers already use image stacking to reject any number of transient artifacts, like satellites, airplanes, cosmic rays, etc.
Third, while these constellations are going to greatly increase the number of satellites in orbit, it's only by about an order of magnitude. Yes, that's worse, but it's not like it's a problem that hasn't existed before.
The type of observations that are likely to be most affected are surveys that actually search for moving near-Earth objects, especially near the Sun (and radio astronomy which apparently can detect terrestrial emissions scattering off of satellites) but I fail to see how this will mean anything like "the end of astronomy" (and I have a Ph.D. in astronomy.)
As new launch systems like Falcon 9, Starship, New Glenn and New Armstrong eliminate these constraints it will eventually be cheaper to build telescopes in space than on the ground.
Other “pusher” motivations include worsening access to real estate, reduced control over light pollution, recognition of indigenous rights, etc.
I don't think the next 5-10 companies launching constellation satellites will be quite as considerate, so one order of magnitude could creep on to two over 15 years.
I think image stacking has been simulated to work somewhere from okay to unusable even for 15s exposures - I think the trails are actually pretty bad due both due to quantity, velocity in the sky, and brighter-fatter.
A very simple and common way is to stack all of the static images aligned on top of each other such that you have a set of values for each pixel corresponding to the same region of sky. Then sort the values of each pixel by brightness and keep the median value for that pixel. Or throw out that top and bottom 10% and average the rest, or throw out the top and bottom N, etc.
This is a standard feature of essentially all astronomical image processing software and has been for a long time.
Remember you don't need to throw away the whole frame, only the pixels that were obstructed. One track across a frame will obstruct less than 1% of the data in that frame.
A generation or two in the future astronomy will probably get redefined quite a bit via remote telescopes and adventure vacations to space and so forth.
Even now there are plenty of enthusiasts who are excited to take pictures of rockets during take off or explore satellites as they pass by. So it actually get more people interested in space and astronomy.
And there will always be people on either side supporting or opposing technological advances - as we have seen thought history. The one thing that is certain in my opinion though is that things will change.
Does the proliferation of high speed Internet to every part of the world outweigh the cheapness of current land based astronomy tooling?
If not, maybe spacex can compensate by providing some launch load for space bound telescopes.
Tonight. And what about when SpaceX gets all 11,000 satellites up there? And then Amazon's constellation. and then all the other American companies planning to do the same thing. And the European companies. And the Chinese companies and the Indian companies, and on and on and on.
Dropping a piece of plastic in a lake isn't a big deal. Until it's 11,000 pieces of plastic. And then hundreds of other people do it, too.
The satellites are not in sunlight unless the sun is not that far below the horizon.
Creating a livable planet is not easy, but nationalistic thinking makes it a hundred times harder.
I'd go with #1.
2. I'd go with #2.
3. Even if #1 is right, jumping to the conclusion that Musk's project is a good idea is a complete non-sequitur. As far as I know, no one has argued that putting 10000 satellites into space is the only way to provide widely available cheaper internet. As you can see from discussions elsewhere in the thread, it's not likely to even do that. Will SpaceX provide service to China?
You mean..."Science"?
Meanwhile, what kind of useful science do you think can be facilitated by globally accessible high-speed internet? The value generated by such a network is clearly orders of magnitude more useful than observing the cosmos, at this juncture of human endeavor. Not too mention that Starlink will allow SpaceX to re-invest more and more money into space launches / space travel. I'd much prefer humans actually visit other celestial bodies rather than just staring at them.
Is this Hacker News? This is the type of nonsense I expect on the NYTimes comment section.
> I'd much rather have humans enjoy nature than writing about it on the internet.
Why are you here instead of enjoying nature?
Astronomy is nice too, but I will choose the internet every time, if forced to choose. We have wonderful images of the whole sky in all kinds of spectrum in incredible resolution.
Starlink means you can be doing research in the middle of the Amazon and have good internet. Antarctica. Middle of the ocean. Wherever. Sure, population centres are all connected to the internet by now, but that's really not what I'm talking about.
Also, a good way to make internet cheaper (so that those in poverty have access) is to provide more alternatives to access / competition.
Likewise, those in poverty living far from population centres (by the way, those are the places with most of the people) are better served by being gifted 10 bricks so they can build an actual stove.
It's built for whoever gets utility out of it and will pay for it, those "noble cases" included. It's not for them, but it enables them.
The internet can tell you how to build a better stove, farm better, raise animals better, discourage you from barbaric rituals that don't actually have the effect you believe them to have, etc. Arguably the poorest, most ignorant of the world are the same people that need the knowledge the internet can provide the most.
Internet access gives you access to actual knowledge. Yes, it also gives access to fake news and farmville, but I think those latter concerns are less important when you are having sex with babies to make your AIDS go away.
That doesn't really answer my question though, but that's probably my fault for using a word as subjective as "useful", so let me rephrase:
How has astronomical knowledge of the CMBR/Big Bang/Black Holes/Pulsars/Galaxies/etc. fundamentally improved the human condition? What specifically have we been able to do (not "know") that we would not have been able to do without terrestrial astronomy?
In the last 100 years, advances in particle physics have been aided by our study of high-energy mechanisms in the universe (nuclear fusion in star systems, supernovae, acceleration of the expansion of the universe, etc.)..
so you have internet thanks, in part, to astronomy..
what a silly comment..
Ditto for everything else on that list. We made discoveries by looking at things and performing experiments here on earth and then realized that these things must be what is causing X and Y out in the cosmos.
The first major breakthroughs for understanding nuclear fusion came because we wanted to understand what powered the Sun and Stars: https://en.wikipedia.org/wiki/Timeline_of_nuclear_fusion
.. and these events began 100 years ago.
Part of what you say is true, we make discoveries by looking at things.. Astronomy gives us more things to look at, and in energy regimes that cost many $$ to replicate in experiments on Earth..
Without Einstein's E = mc^2, Arthur Eddington would not have realized that the fusing of nuclei could power the sun. In other words, he realized that fusing two atoms would release a lot of energy thanks to terrestrial research, and then hypothesized that this is what must power the sun. He did not come to this theory from staring at the sun through a telescope. Astronomy clearly did not lead to fusion - atomic theory did, which did not come from astronomy.
And neither did Einstein formulate E = mc^2 because he was an avid astronomer who wanted to understand the sun.
I am well aware this happened more than 100 years ago, not sure why you would be under the impression that I thought otherwise or needed to hear that for some reason.
If you mass produced space telescopes they wouldn't cost the ridiculous sums spent on JWST, which is a terrible example of the wasteful cost plus contracts of nasa. They've been planning it since 1996, and costs have risen from 1 billion to 10 billion.
Although I doubt that would provide meaningful data to professional astronomer.
https://en.wikipedia.org/wiki/Vantablack
https://culturehustle.com/collections/black/products/black-3...
But odds are they're only going as far as is required, which would be "no brighter than typical satellites" - right?
From the Vantablack wikipedia article:
When light strikes Vantablack, instead of bouncing off, it becomes trapped and is continually deflected amongst the tubes, eventually becoming absorbed and dissipating into heat.[7]
Dealing with heat in space isn't easy, since you have no air to dissipate heat into.
Oops that's classified. But probably such satellites need a dedicated cooling system.
It's never as easy as, just paint it black and hope for the best.
For non spy satellites where stealth isn't one of the top goals, that might mean people don't do it.
Also, typically one does not simply ask a surveillance agency how they do things. They would probably respond with something like, "NO SUCH PERSON AT THIS ADDRESS, RETURN TO SENDER."
Could work without extra cooling...
- needs to survive vacuum
- needs to survive atomic oxygen, that does show up at low Earth orbital altitudes
- needs to handle the thermal cycling as the satellite goes in and out of Earths shadow
- needs to survive unfiltered sunlight without any atmospheric convection to normalize temperature
- needs to avoid overheating the part of the satellite it is covering
- should not emit particles, that could collide with other satellites
- needs to keeps doing this for about 5 years (design lifetime of individual Starlink satellites)
- should harmlessly burn up on satellite reantry
If the given material can do all the above, while still keeping it's desirable properties, then it can be used on a Starlink satellite. :)
Overheating is definitely a big concern for painting your satellite back. There is a lot of work that goes in to thermal design of satellites and that surfaces have the proper optical properties for absorption, reflection and emission.
[1] http://www.eurekamagazine.co.uk/design-engineering-news/worl...
Another question.. if you are building a radio telescope in space, could you just use a thin foil that folds out like origami for the reflector?
What really needs to happen is the ability to build mirrors in LEO so they don't have to be built to survive the launch.
If the BFR (the rocket behind the starship) is successful then yes it could mean the ability to launch very large telescopes in to space. The scientific community would be very exited about this possibility. However, this doesn't necessarily make it very low cost. One launch of the BFR would still likely be much more than an a Falcon Heavy launch.
> if you are building a radio telescope in space, could you just use a thin foil that folds out like origami for the reflector?
Yes! This technology already exists and it is really pretty amazing to see in action. Right now most of them are used on communications satellites or for synthetic aperture radar satellites. See the videos below:
Animation of the radar antenna on SMAP:
https://smap.jpl.nasa.gov/resources/83/smap-antenna-deployme...
Actual video of a large communcations antenna (12m diameter) being deployed. Skip ahead to ~2:15 for the actual unfurling.
https://www.youtube.com/watch?v=_mFnNDzxKFk&feature=emb_titl...
BFR isn't a name that's still in use. Poster you're responding to was correct in calling it Starship: "SpaceX's Starship spacecraft and Super Heavy rocket (collectively referred to as Starship)" (from https://www.spacex.com/starship).
Starship projects to be significantly less expensive than Falcon Heavy _or_ Falcon 9. With total reusability of both stages and a construction built toward little to no refurbish or rehab, the cost per launch is nearly completely dictated (order of magnitude) by fuel costs, and project to be ~$2 million. This is an order of magnitude reduction in $/kg over the Falcon 9.
https://www.space.com/spacex-starship-flight-passenger-cost-...
As a side note, I don't really believe the $2 million price tag either based on my own experiences. Mission specific planning/services/verification tend to push prices of launches 10s of millions of dollars above the "sticker prices" that SpaceX puts on their website.
Nothing against SpaceX, I am a fan of everything they have done to decrease launch costs. They have significantly changed the game in terms of lowering launch costs. But it is really hard to take Elon's wild numbers that he gives the press at face value.
[1] https://www.theverge.com/2018/9/18/17873332/spacex-elon-musk...
A high-quality 24" or 1-meter university-grade observatory telescope can be had for well under $1 million. If you multiply that by a factor of 100 to mount it on a satellite, you're still at 'just' $0.1 billion and can buy a whole Ariane-5 launch just like the JWST to put it at your desired orbit for $0.15B, for a total of $0.25B (a Falcon Heavy runs about half the cost for a launch). You could launch 30 of those (hopefully improving your factor-of-100 cost increase to something more manageable) for less than what the JWST will cost.
I get that JWST is a 6.5 meter telescope, not a piddly backyard 24" device, but why do we have to launch the best single scope possible?
There are only 7 visible-light space telescopes listed at https://en.wikipedia.org/wiki/List_of_space_telescopes#Visib.... I wish there were 70 or 700, with live Internet feeds.
JWST is not the first IR telescope (Spitzer Space telescope, retiring this month comes to mind, 0.85 m diameter primary), but its size will allow both improved resolution (diffraction limit falls like 1/diameter) and improved collection efficiency (grows like diameter^2). Without constellation-flying and interferometric telescopes (see Keck Observatory), one cannot get either one from an array of small telescopes.
There are a lot of scientists grumpy about JWST because of its huge budget, but as long as JWST works, the view it gives of our universe will be spectacular. At this point, I think everyone really wants JWST to work, as so much has been sacrificed to make it possible.
Making things survive in space is hard. Working functionally for the lifespan of the telescope is really hard. There's not a lot you can do once it's up there.
Perhaps a review of telescope design is in order: https://en.wikipedia.org/wiki/Telescope https://en.wikipedia.org/wiki/Optical_telescope
Building large telescopes is hard enough. Putting them in orbit just adds to all the costs. Look at the James Webb Telescope (which still hasn't been launched). https://en.wikipedia.org/wiki/James_Webb_Space_Telescope
It seems possible to launch multiple small telescopes and operate them as one large scope using aperture synthesis. I don't know if there are any existing designs or plans for this.
Also: somewhat ninja'd, see other replies as well.
We know how to do that in radio (VLBI), have some experience in IR (ALMA), are doing research on how to do that in optical. But in practice that is much harder than you think. The relative distances of the telescopes have to be known and constant to within a few fractions of the wavelength you are using. Hard when you are using centimeter radiowaves, insanely hard with optical light that has 600 nanometers wavelength.
That thought exercise should give you 90% of the answers to your question. The atmosphere and light pollution from cities are pretty easy to counteract with location and bigger optics.
These telescopes essentially work by capturing photon counts on a sensor. The individual pixels on the sensor have a limit to the number of photons they can count. You could theoretically subtract the satellite pixel-count values from the photon counts to get rid of the trails. The two problems I see are: 1) You don't know the correct counts for the satellites and I'm not sure how you could get them. 2) The trails will probably saturate the pixels anyway (which can also cause bleeding into other pixels), in which case you just don't have the data of what's 'behind' the trails.
Problem is: With photon count the uncertainty in the number of photons also goes up (the relative error goes down). So even if you know that you should have received 100 photons from the satellite (and have not reached the overflow of 256 in this example yet), Poisson statistics means you will actually get anything between 90 and 110 photons. So if you subtract 100 you have an uncertainty of plus or minus 10 photons left. That is deadly if you astronomical source only gave you 2 photons in that pixel in that time.
I mean to use it like auto-dimming mirrors, or smart headlights. Block the bright stuff that you can easily predict, so you can protect the sensitive image sensors from over-saturating on garbage.
I'm using this data to power my site that shows when you can see Starlink yourself: https://james.darpinian.com/satellites/?special=starlink-lat...
Yes. There's only one other (public) source, https://space-track.org/ which publishes tracking results from US military radars. But the tracking results aren't as accurate as the satellites' own telemetry data.
To do it you'd need a screen in front of the sensor that could occlude the pixels that the Starlink sats were passing over..
One such technology is the optical vortex coronograph. Several types exist.
Most things have trade-offs. Hopefully, the reduced cost of access to space will allow launching of more space-based telescopes, which don't have problems with atmosphere. Any astronomers here that care to explain what only ground-based observatories can do?
Probably you'd want a fairing that holds the mirror on edge, so that it travels edge first as if looking to the side during launch. This would save on air resistance during launch.
There are more issues than just sheer mirror size in this case.
- Resistance to vibrations is a _major_ issue if the mirror is monolithic (as with HST) as opposed to segmented (as with JWST).
- The mirror also has to either be very resistant to extreme temperature changes (and the contraction that comes with it), or must be cooled before launch. For extremely large mirrors, the cooling assembly would add _tons_ of extra weight, since this would most likely be active/liquefied gas cooling, and the weight of the cooling medium alone would be significant in this case.
- Using a shape that's close to being a cylinder is great for cooling too, because cylinders have a very good surface area-to-volume ratio, which matters when you have to account for heat exchange. If memory serves, only ellipsoids are better (with spheroids being a better than ellipsoids, and spheres being ideal).
- The support structure for the mirror (the satellite fuselage proper) would probably have to fit in there too, at least for the first launch. That's not small, even though it can be made collapsible.
- All of the optical elements have to stay outstandingly precisely positioned within insanely tight tolerances. Any shifting could result in a lack of clarity, chromatic aberrations, or other issues, even if the mirror(s) aren't directly warped or damaged.
Even accounting for that, a fairing that's irregular around the long axis of the rocket is often undesirable. While it reduces (compared to the alternative), it can cause issues with rolling after launch, and introduces additional complexity.
Assembling from pieces on the other hand, is more doable.
I would assume a micro gravity only mirror could be much thinner & thus easier to cool down. Or possible alternative techniques could be used to get the needed reflective surface geometry if it does not need to take gravity and atmosphere into account.
edit: book -> novel
A hollow toroid could be spun to provide force and the liquid would naturally form a parabola.
There've been a few experiments on earth and it could have huge cost saving potential in space. Instead of having to launch a 8m+ solid mirror machined to perfection, you could launch a lightweight toroidal substructure with a vat of reflective liquid at a fraction of the cost.
I'm as much a fan of astronomy as anyone, but I'm not willing to let it block the best chance we currently have of becoming a space-faring species. The comm satellites aren't important, but the launch capacity scaling is.
That might close the window of opportunity and not give us a second chance. So better not risk it. :-)
Never mind the problem of us being one asteroid strike or supervolcano away from a cataclysm, and that's not an if but a when.
I have a feeling that for humans to transcend the proverbial great filter, we have to tap into the vast quantities of resources and energy in the solar system, but more importantly rekindle the pioneering era that last ended with the industrial revolution.
The expensive part of the space industry is lifting infrastructure from ground to space. Moving within the solar system is comparatively cheap if we avoid descending into the gravity well of other planets. Luckily, this is unnecessary for most asteroid mining.
Humankind experienced incredible advances with the toppling of every transportational frontier. The wheel, seafaring, motorized transport and flight all resulted in expansions lasting a hundred years each.
The next frontier is the solar system. We don't know if we'll be able to ever leave it, but that's irrelevant because it can be our home for the next billion years. Our best shot at actually preserving the habitability of Earth is exploiting resources out in space.
In fact, I'm pretty sure both "sides" would benefit greatly from cooperating. It might even be that these aren't "sides" but just different cousins of the family with different outlooks on their own life, and we need a little bit of everything, and everyone, to make a world.
Many kilometers in diameter in circumference should be possible and likely much more. The whole thing would at the same time be likely really really light, just thin stabilized foil, as it does not need to fight gravity or survive launch loads. Could be quite a sight. :)
>Many kilometers in diameter in circumference should be possible and likely much more.
This is a misconception. There is plenty of "gravity". The mirror has to keep a very precise shape and attitude, which severely limits the possible size, considering it has to be light and is a subject to gravitational perturbations. Large and thin constructions in space (solar panels, antennas etc) are mechanically non-trivial on their own, and for telescope-quality mirrors it seems downright impossible.
But in the short-medium term, the cheapest course that delivers is to use normal telescopes and interferometry (say on some orbit between Venus and Mars). I'm pretty sure it's also a domain where narrow AI may help because finding "anomalies" in space is a lot like finding anomalies on X-rays to find malignant tumors — something AI apparently can do well. Both problems fit incredibly large datasets + ultra low resolution of said anomalous blobs, and discrepancy with normal ones barely statistically significant (well below what human eyes may spot).
This is how I see the immediate future of space-based observation: lots of small things that cooperate extremely (increasingly) well with each other, "networks" more than "giants", much like down here on the ground.
It's just easier, cheaper, and lets you grab a lot of low-hanging fruits. Meanwhile, space-based fabrication can kick off and take the time to reach 'self-sustaining' velocity.
And astronomy is still an extremely important component for becoming space-faring. No use in going somewhere blindly when you can have a look first. But if there is no-one looking because nothing to see, funding dried up, scientists demotivated,...
[1]https://www.space.com/22505-worlds-largest-telescopes-explai...
Shipping complicated physical hardware to space requires that it absolutely must work on the first try, and never require maintenance for the lifetime of the instrument. In contrast, the large earth-based telescopes can be regularly updated, maintained, and debugged. Access for such activities costs as much as a plane ticket to Chile, instead of a dedicated mission to space.
1. Bigass telescopes. Some radio telescopes are 100 or even 1000 feet across. You can't put something like that easily in a rocket fairing. JWST has a 20 foot mirror and they probably spent hundreds of millions of dollars figuring out how to fit that thing in an Arianne 5.
2. Easy maintenance and upgrades. There are 80 year old telescopes still doing useful science since you can make incremental upgrades over the years. (shoutout to Hubble: at 30 I think it's probably the longest lived space telescope, even if it's getting a bit long in the tooth)
3. Interferometry. This would potentially be really cool to do in space, since you could theoretically make a telescope whose diameter is tens of thousands of miles. However, interferometry requires you to be able to position yourself really accurately (amount of accuracy you need depends on wavelength and a few other factors, but potentially at the micro-meter level). That's really hard to do in space.
4. You can build a bunch of ground based observatories for the cost of a single space one.
5. Data downlink. Some telescopes generate a lot of data. It's not easy to get a terabit per second of data down to the ground.
Maybe even become a net positive for astronomy? Since the volume and density of the data collected would increase as the fleet grows, the value presumably increases as well, hopefully faster than the problems that they create.
If you can't solve that problem, then I don't think it's worth it just so some first world folks can YouTube when camping.
But there are many poor countries with rural areas that have almost no Internet access and would greatly profit from it. Starlink seems to be especially useful for people in those areas.
Radio is firmly ground based, because you need huge dishes and potentially many (thousands) of them, at very precisely known distances.
IR is mostly space based (with SOFIA and ALMA the notable exception) because of atmospheric absorption.
Optical is firmly ground based, due to much lower cost for large telescopes. (See https://doi.org/10.1117/1.2031216 for the factors that affect cost). The notable exceptions are Hubble and satellites monitoring the sun such as Stereo and SDO.
X-Ray is space based again due to atmosphere.
Gamma-ray telescopes are an interesting mix between ground based air cherenkov telescopes (IACTs such as Hess, Magic and Veritas) and water cherenkov detektors such as HAWK and space based Fermi (with relatively poor sensitivity and low upper energy cut off, but very wide field of view).
Neutrino detectors are firmly ground based because the need huge detectors (the cubic kilometer of icecube is basically the lower limit).
So they are very much complementary. And some things will probably never moved to space, even if launch was free.
https://en.wikipedia.org/wiki/Very-long-baseline_interferome...
http://www.asc.rssi.ru/radioastron/news/newsl/en/newsl_36_en...
[1] http://www.stsci.edu/%7Ewebdocs/STScINewsletter/2003/spring_...
No sparkles any more I want them to turn black.
At least SpaceX seems to be taking these concerns a little seriously.
Also, wasn't there a sci-fi TV show not that long ago that was popular on HN that had a theme song along the lines of "They can't take the sky from me?" I guess the lyricist was wrong.
Also interesting how people who could not find the big dipper think that removing the streaks is "just basic image processing" without knowing anything how modern astronomy is done. Never mind that professional astronomers are complaining. Oh and of course you get suggestions like "you can just fill a 30 km bubble with gas in space and use that". As another commenter put it nicely "everything is trivial when it is somebody else problem".
That's like saying "Sure, let the giant industrial conglomerate dump toxins in the drinking water. That way it can earn enough money to build a machine to clean the water up and sell it back to us and everyone will be happy!"
Why not just not pollute the water in the first place?
This is a forum for engineers (for a broad sense of engineer). We like to talk about technology. We like to speculate about the future and about politics. Starlink is a cool idea, so it's not surprising there's enthusiasm for it.
We should not be put in control of anything, ever. If that weren't already common sense, you'd just need to put half a dozen policy threads from Hacker News in front of a congressional committee to have them warning of the dire effects of engineer influence. Stuff we create should be heavily regulated when it attempts to "disrupt" society, like Uber or a lot of Silicon Valley startups.
Uncharitably, you might say HN has a ton of Dunning-Kruger about anything not directly technology related. I wouldn't put it that way: it's everyone's right to speculate about politics, the future, and values, but most people here don't actually think they should be put in charge of anything.
It's even worse. It is people thinking that because they are brilliant in some technical field (JS frameworks, or compilers, or machine learning or whatever) they are also brilliant in every other technical field (be it astronomy, high performance computing or medicine).
But there's another dimension, which is that Starlink is supposed to be funding the only company that's materially doing anything new in the domain of spaceflight technology. For a bunch of nerds who grew up drenched in science fiction and promises of humanity's bright future in space, who've instead seen decades of regression in capabilities, and who live in the same world where my first paragraph is true ... that's very meaningful, far beyond the "fanboy" slur.
Not saying I come down on either side of the Starlink should/should not exist fence, but I think the motives and attitudes of its proponents are often misrepresented and that's no way to have a productive conversation about it.
These lunatic leaders are taking it too far. I will have to put on my superhero coat soon, and create some balance
We are also coming to a point where we have to acknowledge that sky is changing and astronomy or where we place telescopes should change. Depending on what is being observed.